Duo signed a lease Thursday for larger office space in downtown Ann Arbor. It plans to make the move into 14,000 square feet at 123 N. Ashley St., spread over three floors, sometime in the fourth quarter.

CEO Dug Song, who co-founded the company in 2009, said he has been hiring steadily and plans to be near 100 employees by year's end.

Duo Security provides two-factor authentication — which verifies the identity of an entity trying to access services in a computer or network — to more than 4,000 organizations worldwide.

Song was a member of the 2012 class of Crain's 40 Under 40. In 2000, he was one of five self-described geeks and hackers who co-founded Arbor Networks, a University of Michigan spinoff that was later sold to Tektronix Communications.

Arbor Networks' security software is used by more than 80 percent of the world's Internet providers.

Song co-founded the Tech Brewery, an Ann Arbor tech incubator, and is one of the organizers of a 30,000-square-foot skate park, slated to open June 21, at Veterans Memorial Park in Ann Arbor.